It is often acknowledged that public policies can constrain people's procreative opportunities, in some cases even infringing their procreative rights. However, a topic that is not often discussed is how the procreative choices of one generation can affect the procreative opportunities of later generations. In this article, we argue that the demographic fact that childbearing above the replacement fertility level is eventually unsustainable supports two constraints on universal procreation rights: a compossibility constraint and an egalitarian constraint. We explore the implications of these two constraints and suggest that there are reasons to think of procreative opportunity as a finite resource that can be distributed more or less equally across generations. We also briefly discuss possible ways of meeting demands of intergenerational justice with respect to procreative opportunity.